Did you ever wonder why bread that’s left over becomes hard and dry, or why rice gets grainy when it’s been in the fridge for a while? Well, it’s because of something interesting called starch retrogradation. This is a natural process that happens in foods with a lot of starch (like bread and rice), and it’s what causes the texture to change and the food to not taste as fresh as before. It’s like the reason why food becomes “stale.”

In this blog post, we will discuss starch retrogradation, exploring its science, effects on food, and how to minimize its impact on our culinary delights.

UNDERSTANDING RETROGRADATION

Starch is the most common carbohydrate in plants. It is made up of two kinds of molecules: amylose and amylopectin. Amylose is arranged in a straight chain, while amylopectin has a more complex, branched structure. I’ve written another article that talks about how these two differ. You can find it here. When we cook or work with starchy foods, the starch molecules soak up water and expand, which is why dishes can become thicker and turn into a gel-like texture.

On the flip side, retrogradation stands as the process wherein starch molecules within cooked foods undergo a reorganization, adopting a more structured and crystalline arrangement. This intricate occurrence takes place when gelatinized starch gradually cools and sheds moisture, compelling the starch chains to bond and reform crystals. Consequently, the once tender and vibrant texture of the food undergoes a shift, losing its initial allure.

High amylose starches are predisposed to undergo retrogradation. This phenomenon becomes evident in baked goods that lose their initial fresh taste and texture, signifying the transition from a gel-like starch state. Similarly, residual long-grain rice experiences this process due to its elevated amylose content, causing it to become rigid and less palatable.

Several factors impact the speed of retrogradation. These include the ratio of amylose to amylopectin molecules, which form the starch; the way these molecules are structured due to the plant source of the starch; temperature; how concentrated the starch is; and the existence and amount of other components, especially surfactants and salts.

THE SCIENCE BEHIND THE PROCESS

Starch retrogradation initiates promptly after the baking phase concludes and the product commences its cooling journey. This phenomenon is particularly pronounced in products containing a high concentration of amylose starch. Amylose, a linear starch molecule, undergoes retrogradation more swiftly than its counterpart, amylopectin. Notably, by the time the baked product reaches room temperature, the process of amylose retrogradation is often nearing completion.

However, the story doesn’t end there. The retrogradation of amylopectin, a branched starch molecule, requires a more extended period compared to amylose retrogradation. This temporal discrepancy between the two starch components imparts a significant impact on the overall quality of baked goods, contributing significantly to the phenomenon known as staling.

Staling, the undesirable transformation of baked goods from their fresh and soft state to a more rigid and less palatable one, is predominantly driven by the retrogradation of amylopectin. Over time, during the staling phase, the once pliable and amorphous amylopectin molecules revert to their original crystalline state, forming rigid granular structures. This process results in the expulsion of moisture from the product’s crumb, causing a loss of moisture content.

As a consequence of the expelled moisture, the texture of the baked product undergoes a noticeable change. The product gradually becomes firmer and less elastic, a stark departure from its desirable characteristics. This loss of moisture and alteration in texture are key attributes of staling, rendering the product less appealing to consumers.

COMMON FOODS THAT UNDERGOES STARCH DEGRADATION

Starch retrogradation is something that happens to many common foods we eat. Let’s take a look at some examples: bread, pasta, rice, potatoes, and crackers.

Think about bread. When it’s fresh out of the oven, it’s soft and chewy. But as it sits for a while, it becomes dry and crumbly. Even the outside part, the crust, turns tough and less yummy.

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Pasta is another example. When you cook pasta and it’s hot, it’s nice and soft with a little bit of chewiness. But as it cools down, it starts getting harder and not as tasty. That’s why leftover pasta isn’t as good – it loses its good texture.

Rice also goes through changes. Right after you cook rice, it’s fluffy and moist. But as it gets cold, it becomes dry and the grains might stick together, making it not so great to eat.

Potatoes, like the ones you might have as fries or mashed, also change. After they’re cooked and then cool, they can turn from creamy and soft to kind of gritty and dry. That’s not as yummy.

And let’s not forget crackers. When they’re fresh, they’re crunchy and easy to break. But if you leave them out, they get softer and chewier over time.

These foods show us how starch retrogradation works. It’s like they’re going through a texture change after they’re cooked and then cool down. So, if your sandwich bread isn’t as soft or your pasta isn’t as good the next day, you can blame starch retrogradation for that!

FIGHTING STALING IN THE FOOD INDUSTRY

Emulsifiers, enzymes, and hydrocolloids emerge as key players in this pursuit, each wielding distinct functions that contribute to the modification of the retrogradation process, ultimately enhancing product quality and extending shelf life.

By dispersing fat molecules within a starch matrix, emulsifiers hinder the reassociation of starch molecules into a crystalline structure. Consider mayonnaise, a classic example of an emulsion. When emulsifiers are introduced, the resulting product showcases reduced starch retrogradation, leading to a smoother, longer-lasting consistency that defies the clumping and firming often associated with retrograded starches.

Another example of emulsier is glycerol monostearate (GMS). GMS is produced by adding glycerol to fat or oil which results in a mixture of monoglyceride and diglyceride. Incorporating GMS at 0.25–0.5% allows amylose to form a helical complex that retards the retrogradation of the starch.

Enzymes catalyze specific reactions, transforming complex molecules with precision. In the context of starch retrogradation, enzymes like amylases can break down starch molecules into smaller fragments, impeding their propensity to form rigid crystalline networks upon cooling. This enzymatic intervention not only enhances the texture but also extends the freshness of products. For instance, the addition of amylase enzymes mitigates the retrogradation-induced staling, resulting in loaves that remain softer and more enjoyable over an extended period.

Glycosyltranferase is another enzyme that adds more branching points to create modified starch. This results in enhanced functional characteristics such as increased solubility, decreased viscosity, and minimized retrogradation.

Hydrocolloids, a diverse group of substances with exceptional water-absorbing capabilities, contribute significantly to the fight against starch retrogradation. They do this by preventing the formation of tight crystalline structures during retrogradation. Imagine a fruit pie filling; the incorporation of hydrocolloids maintains the desired consistency and texture, resisting the undesirable textural changes stemming from starch retrogradation.

PREVENTING STALING OF FOOD AT HOME

An effective approach involves appropriate storage methods. For instance, when it comes to baked goods such as bread, placing them in an airtight container or plastic bag within a cool, dry location can effectively delay moisture loss and limit exposure to air. Although some might suggest refrigerating baked items, this might not be the optimal choice, as it could accelerate retrogradation. In fact, staling of bread happens most rapidly at 32°F (0°C) to 39°F (4°C).

For extended preservation, freezing is very effective at slowing down starch retrogradation and staling. However, it’s important to recognize that certain changes in texture may occur during the thawing process. Thus, it is recommended to take these potential alterations into account when planning the use of frozen starchy items.

When reheating starchy leftovers, it’s wise to choose gentle methods that safeguard the original texture. Employ techniques that minimize exposure to high temperatures, such as microwaving with a small amount of water or utilizing mild oven reheating. By adopting these methods, the risk of overcooking and excessive moisture loss is mitigated, ensuring that the starchy foods maintain their desired texture and overall quality.

References:

A. Chakraverty (2014). Postharvest Technology and Food Process Engineering. CRC Press.

W.Zhou, Y. H. Hui (2014). Bakery Products Science and Technology(2nd Edition). John Wiley & Sons, Ltd.

M. Kuddus (2018). Enzymes in Food Technology. Springer.

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

P. Cheung, B. Mehta (2015). Handbook of Food Chemistry. Springer

The post Starch Retrogradation: Understanding the Science Behind Stale Food appeared first on The Food Untold.

While baking soda and powder are in the same category of chemical leaveners, their chemical make up is different. This is why it is not appropriate to replace baking soda with baking powder of the same amount or vice versa. Doing so may result in undesirable changes in the baked product, although results may vary. Instead, the amount is changed and/or added with another ingredient. For example, 1 teaspoon of baking powder is replaced by 1/4 teaspoon of baking soda and 1/2 teaspoon of cream of tartar. Conversely, replace each teaspoon of baking soda with 3 to 4 teaspoons of baking powder, and leave out the cream of tartar.

Baking soda (sodium bicarbonate) is a base that readily reacts with acids to produce carbon dioxide. Citrus juice, buttermilk, yogurt, fruit juice, and cream of tartar are all examples of acid that can be incorporated. It is suggested that up to 1/4 teaspoon of baking soda can be used per cup of flour. Baking powder, on the other hand, combines the base (alkali) and acid in a single powder. For this reason, no acidic ingredient is required. Its inert filling prevents it from from absorbing excess moisture from the atmosphere that would reduce its effectiveness.

To put it simply, baking soda is pure sodium bicarbonate, whereas baking powder contains other ingredients in addition to sodium bicarbonate.

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When choosing a leavening agent, it is important to keep in mind that using the incorrect one can significantly alter the final product of your baked goods. But when do you need one over the other?

HOW CHEMICAL LEAVENING AGENTS WORKS

Most baked products are known for being light and fluffy. These are made possible by the addition of leavening or rising agents. Leavening is the foaming action caused by the incorporation of either air or carbon dioxide bubbles into doughs and batters. They can be categorized into three forms: biological, chemical, and physical.

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Baking soda and baking powder are both chemical leaveners. Both of these leaveners can chemically react to produce carbon dioxide gas. But their chemical make up affects how they are used. During baking, the expanding gas bubbles they produce become trapped in the structure of the dough or batter as the gluten structure and dough volume increase. This turns the dough into a sponge. The finished product has a tender and porous texture after baking.

BAKING SODA OR BAKING POWDER?

Some recipes call for baking soda, others for baking powder, while some call for both. What factors influence your decision? Well, it is primarily determined by the desired final product characteristics. Generally, baking powder will provide a higher rise, but baking soda will give you a flatter or browner structure, like that in a chocolate chip cookie.

The baking soda causes the cookies to brown and spread out on the pan rather than floating in the air. Baking powder cookies will taste more cake-like than baking soda cookies due to the rise. If a cake-like cookie is desired, it will be necessary to add more baking powder to a baking soda-based cookie recipe because baking soda only contains about a third of the same amount of baking powder. Another reason to use baking soda is if there a need to neutralize acidic ingredient such as yogurt or buttermilk.

If a recipe calls for both leavening agents, the product is actually being leavened by the baking powder. This contains the appropriate proportion so the acids present react with the bicarbonate. The role of baking soda here is neutralize the acid present in the mixture to avoid a sour overtone. The presence of both leavening agents allows for an even distribution of rise throughout the final product.

In some recipes, buttermilk is used instead of just milk. Yes, there is no need for an acid, but buttermilk is thick. Not only it provides milk proteins that interfere with gluten, it also reduces its development. This significantly reduces the amount of flour needed when added to batter.

If a recipe contains Dutch-processed or alkalized cocoa powder, it is often partnered with baking powder. The pH or acidity level of alkalized cocoa powder is near neutral. Hence, it does not react with baking soda.

The post Is Baking Soda And Baking Powder The Same? appeared first on The Food Untold.

Flour is a product of milling. This means it is already in a fine particle form. Back in the early days of flour making, the raw grain, like barley, would be pounded with rocks until it was as fine as possible. But it would be far coarser than today’s standard. Flour particles are now processed and sorted to less than a quarter of a millimeter in size. The flour classification is determined by sifting.

The varieties of flour obtained range from patent flour to straight flour, and the flour streams range from fine or first break to coarse or clear. Depending on how much of the whole endosperm was milled, patent flour is classified as long, medium, or short. Short patents come from the endosperm’s center and are high in starch. They are ideal for creating pastry flour.

With that being said, is it necessary to sift flour during ingredients preparation? Well, it is. But not to break down wheat starch. Sifting flour actually does several things to help you produce baked goods properly. Among these are to incorporate air as a leavener, sift out foreign objects, and more importantly, break up lumps.

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But not all baked products require sifting, especially if the baker only wants to correct the particles that have clumped together by settling. Take bread making, for example. Preparing flour by sifting for making bread makes no difference. This is because kneading presses the flour together.

Anyway, let’s discuss all what sifting flour does further.

INCORPORATION OF AIR AS A LEAVENER

A leavener or leavening agent is a key ingredient in baking that helps dough or batter to rise and expand. Without one, a baked product would be dense and low in volume. Common leaveners are microorganisms such as yeast and lactic acid bacteria or chemical-based baking soda or baking powder. The rising effect can also happen by incorporating air through sifting flour with other dry ingredients.

In fact, air is the first leavening agent added to the cake batter. Many angel food cake recipes call for sifting the flour and sugar at least four times to guarantee appropriate air incorporation. A hassle, right? The book Science of Good Cooking by America’s Test Kitchen figured that processing the flour with half the sugar in a food processor makes sifting flour just once works.

The amount of air depends several factors. These include the mixing procedure, such as sifting of flour before adding it, beating, creaming, and so on. As a result, the amount of air that is integrated into a batter or dough combination might vary greatly.

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The creaming of fat and sugar is another process that uses air. The fat (plastic fat) aids in the incorporation and trapping of air in the batter, as well as the dispersion of air cells into small units. The product rises as air is released during heating.

SIFTING OUT FOREIGN OBJECTS

Sifting dry materials is required while preparing dough ingredients to ensure that no foreign matter is contained in the dough. In large scale baking, a bar magnet is present in the screening apparatus to remove any metal impurities. Small or trace amounts of substances must be dissolved or suspended in water before being added to flour.

Truth is manufacturing of flour has gone a long way since our ancestors first produce it by pounding it with stone. The flour produced nowadays is free from extraneous items such as husks and insects. So flour that we buy from the supermarket is free from foreign materials and other contaminants.

Well, unless there has been poor handling or storage prior to use.

BREAKIN UP LUMPS IN THE FLOUR

The main objective of sifting flour is to break up any lumps that have formed. Doing so help get an accurate measurement of the ingredient. As you can now see, sifting flour is necessary.

Sifting powdered ingredients into a cake mix disperses them and raises the amount of the flour. If left unsifted, the little clumps of flour stay together in thick clusters once water is introduced. And the clumps are difficult to break up with stirring and whisking. These aggregates thicken the walls of the small bubbles in the batter, weighing them down and resulting in a denser sponge.

Furthermore, sifting ensures consistency in product preparation by standardizing the amount of flour added to a recipe. When ingredients are weighed rather than measured, consistency is more likely. Sifting reduces the amount of flour that goes into the recipe.

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1 cup of sifted cake flour weighs approximately 3 ounces, whereas 1 cup of unsifted cake flour measured directly from the bin weighs approximately 4 ounces. Hence, one will end up with too much (or far too little) flour. To ensure the correct amount of flour, if the recipe call for “1 cup sifted flour,” sift the flour directly into a measuring cup set on top of parchment paper and level off excess flour.

In some recipes, you may encounter instructions “flour, sifted” and “sifted flour”. These are two different instructions. The former is measure first, then sift; the latter is sift first, then measure.

References:

W. Zhou, Y. H. Hui, I. DeLyn, M. A. Pagani, C. M. Rosell, J. Selman, N. Therdthai (2014). Bakery Products Science and Technology (2nd edition). John Wiley & Sons, Ltd.

M. Gibson (2018). Food Science and the Culinary Arts. Academic Press.

America’s Test Kitchen (2012). The Science of Good Cooking: Master 50 Simple Concepts to Enjoy a Lifetime of Success in the Kitchen. Cook’s Illustrated.

The post Baking Science: What Does Sifting Flour Do? appeared first on The Food Untold.

Staling is a complicated process that begins shortly after baking and involves a number of physicochemical changes. These are mostly associated with an increase in crumb stiffness and moisture loss. And as a result, there is a loss of eating quality because of flavor, color, and texture deterioration. But it does not mean stale bread has already gone bad. Stale bread still safe to consume, although not as good as freshly baked bread—you would want it soft.

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Some people store bread in the refrigerator to extend its freshness. But the truth is that it only makes things worse, quality-wise. Sure, the temperature inside the refrigerator slows down the growth of microorganisms, but it also speeds up the rate of starch retrogradation, or simply staling (more on this below).

But how to properly make stale bread soft, anyway? To explain better how, a brief explanation of how bread staling occurs should help.

STALING AND RETROGADATION

Bakery products with a crust (mostly bread and cakes) tend to dry out quickly as water migrates from the crumb, resulting in a firmer and drier texture. The crust, on the other hand, tends to become rubbery or soggy. The rate at which these changes occur is determined by storage conditions, crust thickness, and the product’s crust-to-crumb ratio. For most consumers, the condition of the storage area (such as the refrigerator) is the culprit. The maximum staling rate for bread is thought to occur at refrigerated temperatures.

In baking science, these changes occur during starch retrogradation. Starch retrogradation is when starch in bread cools and reverts to a more crystalline structure. Starch granules contain polysaccharides amylose and amylopectin. Both of these may be involved in a textural shift that causes them to become more “gritty” over time. This is evident when warm starch molecules in bread cool, shrink and then firm up in the process of staling.

Starch in freshly baked good, however, is still in existence in gel form. A bread is said to be “fresh” when the starch remains as a gel. When the starch regains its crystalline structure, the product gets firmer and becomes “stale”. In science, this is referred to as starch retrogradation.

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Starch retrogradation is more likely to occur in high amylose starch. This is the same reason why long grain rice, as left over, becomes hard over time. Amylose retrogradation is nearly finished by the time the product has reached room temperature. Amylopectin retrogradation takes longer than amylose retrogradation, and is thus the principal cause of staling.

MAKING STALE BREAD SOFT

Commercial breads are able to prolong their freshness because of the additives they contain. Such ingredients bakers use include emulsifiers or bread softeners such as sodium stearoyl lactylate, monoglycerides, and calcium stearoyl lactylate. They are permitted at a QS level in all baked products, and retard retrogradation during cooling and subsequent storage by binding to the amylose fraction of the wheat starch at raised temperatures.

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Sure, commercial breads stay fresh for longer because of the ingredients they contain, but they become stale eventually. Some people would throw bread that has become stale. That is a wrong habit, though. Luckily, there are a few proven ways to revive stale bread. Here they are:

Reheating in the oven

To do this, turn on the oven and set it at 300ºF (150ºC). Reheat the bread for up to 15 minutes. This will depend on the degree of dryness and the size of the bread. The idea here is to replace the moisture that was lost. So you would want to wrap the bread first in damp towel or brush the crust with water before wrapping it in foil. The steam is retained by the wrapping as the water tries to evaporate. The bread then absorbs the steam to become noticeably softer. The big question is, is reheated bread the same as it was fresh out of the oven?

Definitely no. A freshly baked bread has a soft crumb and a crispy crust. But with a reheated bread, do not expect a crispy crumb.

And remember that the effect of this method works only for an hour or two before starch retrogadation sets in again so immediately consume your revived bread.

Steaming

The process of steaming stale bread is similar reheating in the oven. To do this, bring a pot of water to a boil in a steamer to generate steam. And then place the bread in the steamer for up to 15 minutes, but 5 minutes should usually suffice.

This method works best if the bread is very hard as this produces more moisture and less heat.

References:

W. Zhou, Y. H. Hui, I. DeLyn, M. A. Pagani, C. M. Rosell, J. Selman, N. Therdthai (2014). Bakery Products Science and Technology (2nd edition). John Wiley & Sons, Ltd

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

S. Cauvin, L. Young (1999). Technology of Breadmaking. Aspen Publication, Inc.

M. Gibson (2018). Food Science and the Culinary Arts. Academic Press

The post How To Make Stale Bread Soft? appeared first on The Food Untold.

How do you store sourdough bread? To better answer this question, a little basic bread chemistry should help.

Sourdough breads or doughs are different than typical homemade white bread. They are more tangy and flavorful because they contain an acidic component such as buttermilk, watered-down yogurt, or cultured bacterial “starters.”

Starters are a small bit of dough that was preserved from the last time you made bread. The baker adds a bit more water and flour to the starter and then lets it ferment for a longer amount of time (2-24 hours) before adding the other bread components. This replaces any added “baker’s” yeast and provides the finished product its distinct flavor. There are several sourdoughs around the world, each with its distinct “starter” and flavor.

This depends on several factors such as the combination of bacteria and yeast culture and country of origin. One common bacteria and yeast combination is Lactobacillus sanfrancisco bacteria and Saccharomyces exiguus, a non-bakers yeast. These microorganisms are important during fermentation. The bacteria consume and break down maltose sugar to produce carbon dioxide and acetic and lactic acids. The acids are responsible for the distinct sour taste of sourdough bread. The yeasts also produce bread-leavening carbon dioxide and break down the byproducts of lactic acid fermentation.

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Another characteristic of sourdough bread is the lack of the brown color for a baked product. This is because of increased acidity due to lactic acid production by bacteria and yeast. Browning reactions are slowed down by acidity.

Now that we’ve covered some of the basic things to know about sourdough bread, let’s discuss how it becomes stale and how to store it properly.

HOW SOURDOUGH BREAD STALES

It is worth noting that sourdough bread is different than regular yeast-leavened bread. It has higher hydration. Hence, it contains more moisture in the interior and a more tender and open crumb. Generally, the higher the hydration, the better. It helps delay crust forming, making the crust thinner as it forms.

The higher hydration also helps make the sourdough bread fresh for longer.

Staling starts as soon as the bread cools down after baking. It starts as the crumb begins to degrade as a result of the movement and evaporation of water. During baking, all of the water surrounding the starch travels inward. As the sourdough bread ages, the moisture evaporates, leaving a bread that is still tasty but not as fresh as the day it was baked.

Sourdough bread can be light and fluffy. However, as it ages, it becomes hard and dense. Water migration will continue until there are no more water molecules left for the reaction to occur. Bread that has gone stale will have a hard, dry surface.

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The good thing about sourdough bread is that it does not get moldy as fast as regular yeast-leavened bread. While molds love to live in damp or moist conditions, they do not prefer acidic environments, which sourdough breads are, all thanks to the good bacteria present.

But it is just one factor that preserves the freshness. Remember that sourdough breads are organic—no preservatives at all. Generally, (homemade) sourdough breads are at their peak of freshness within the first 24 hours. But it can last up to 5 days at room temperature.

To preserve sourdough breads and extends their shelf life, they should be properly stored.

METHODS OF STORING SOURDOUGH BREAD

Knowing how to store sourdough bread requires knowledge of its composition and chemistry, which we briefly discussed earlier.

There are several ways to store sourdough bread. But most of these methods have a disadvantage so these should be done properly. For example, wrapping the bread in a foil will prevent or reduce airflow, helping the bread to retain moisture for longer. But the moisture in the bread and the foil makes a great combination for molds to thrive.

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Some prefer to store bread in a paper bag. Paper bags are environmentally friendly, inexpensive, and visually appealing. They allow your bread to “breathe,” enabling moisture to escape gradually. This prevents mold to grow, and the beautiful crust to remain crisp. However, the permeability of a paper bag allows humidity to move. Thus, it will be hard for sourdough bread to maintain a soft inside.

If the bread has been sliced already, leave it on a breadboard cut-side down. This keeps the bread from drying out while preventing any moisture from accumulating on the crust.

If the bread is already on its 5th day, wrap the bread (whole or sliced) with plastic freezer wrap, sealable plastic bag or aluminum foil and store it in the freezer. If properly stored, frozen sourdough bread should maintain its quality up to 3 months. But the shorter the freezing duration, the better because the flavor diminishes over time. Once the bread is ready for use, simply take it out, thaw, and place it in a pre-heated oven.

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One common misconception about storing sourdough bread is that it is fine to store it in the refrigerator. Well, never store leftover sourdough bread in the refrigerator. When bread is refrigerated, the starch molecules in the bread recrystallize considerably more quickly than they would at room temperature. Furthermore, the inside of the refrigerator will dry the bread out.

The post How To Store Sourdough Bread? appeared first on The Food Untold.

Our ancestors enjoyed breads without leavening them. They were basically made of cooked mixture of flour and water, and often added with salt. Today, unleavened breads still do exist. However, there is no denying that people consumed more leavened baked products. The process of leavening occurs when the gluten structure or air spaces is filled with a leavening agent, making the dough or batter to rise and expand during baking. Although carbon dioxide is the primary cause of leavening, other gases, such as ammonia gas, water in the form of steam, and integrated air (added during mixing), also contribute to the expansion of baked goods.

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Leavening can be considered the key step in bread making. Without leavening agents, doughs and batters would be dense and low in volume, resulting in dense baked items. Hence, the aeration in the crumb structure greatly contributes to the sensory assessment and consumer acceptability of bread.

Leavening agents or leaveners are categorized in three forms:

1. Biological
2. Chemical
3. Physical (mechanical)

Let’s discuss each of them.

BIOLOGICAL LEAVENING AGENTS

The biological process of fermentation may produce leavening, in which the bacteria or yeast works to metabolize organic materials that are fermentable.

Bacteria

Lactobacillus sanfrancisco bacteria is an example of this. L. sanfrancisco is a lactic acid bacteria
(LABs), which are a class of gram-positive bacteria that can transform organic acids from carbohydrate sources into a wide variety of metabolites. Organic acids, such as propionic, formic, acetic, and lactic acids, make it difficult for pathogenic and spoilage microorganisms to develop.

Lactic and acetic acids are particularly important during fermentation because they are responsible for producing sourness in sourdough bread.

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Making sourdough bread require the presence of yeast and bacteria in a ratio of about 1:100. When L. sanfrancisco is used, it if often along with Saccharomyces exiguus, a non-baker’s yeast. Depending on the type of flour and the country, different lactic acid bacteria predominate in sourdoughs. Other LABs that may be used in sourdough include Lactobacillus sakei, Leuconostoc mesenteroides, Lactobacillus paracasei, Leuconostoc citreum, and Weissella cibaria.

During fermentation, the bacteria break down maltose, releasing carbon dioxide and acetic and lactic acids in the process which adds taste in the form of sourness, while the yeast produces carbon dioxide that leavens the dough. The yeast breaks down the by-products of lactic acid fermentation, but the lactic acid bacteria can break down carbohydrates that the yeast cannot.

It is usual practice to save starters or sponges of dough from one baking and utilize them in another. These starters or sponges contain both yeast and bacteria.

Yeast

Yeasts are eukaryotic, unicellular microorganisms that belong to the fungi kingdom. Yeasts can be distinguished from bacteria by having larger cells and having cell morphologies like oval, elongate, elliptical, or spherical. Typical yeast cells have a diameter of 5 to 8 μm, while some are significantly larger. Smaller cells are more common in older yeast cultures. The majority of yeasts used in food production split through budding or fission.

Saccharomyces cerevisiae is the most common strain of yeast in making bread. Since ancient times, fermented cereal-based goods have been made using S. cerevisiae. The evolution of the modern baking industry was significantly influenced by its domestication and widespread proliferation.

The Latin name, Saccharomyces cerevisiae, means brewer’s yeast. In the fermentation process that creates bread dough, yeast consumes the starch and sugar found in flour. And it transforms them into carbon dioxide and alcohol. In an anaerobic process, it releases zymase, which breaks down fermentable carbohydrates into ethanol and carbon dioxide (the amount of carbon dioxide produced increases as the number of yeast cells increases). The majority of the alcohol is then volatized in baking, and the carbon dioxide provides the leavening action.

Baker’s yeast comes in three forms: active dry, rapid-rise, and quick yeast. They are most frequently used at home. All of these forms are available in dried form, which is advantageous for home bakers as they have 1 to 2 years of shelf life in the refrigerator.

Commercial bakers frequently use fresh or wet yeast because it is more effective, but it only has a shelf life of two weeks, making it less suitable for home bakers. However, the addition of warm water or milk and the baking process provide the heat and moisture that the yeast requires to become active (for heat).

CHEMICAL LEAVENING AGENTS

Chemical leaveners are intriguing since they start working almost instantly when added to a recipe. In situations where a lengthy biological fermentation is either unfeasible, unneeded, or undesirable, chemical leaveners are substituted instead. Baking soda is a typical chemical leavening agent.

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Baking soda

It is sometimes referred to as sodium bicarbonate or bicarbonate of soda, is a “base” that easily combines with acids to produce carbon dioxide gas. The most common sources of acids added to a baking soda leavened quick bread or muffin are buttermilk or sour cream (lactic acid), molasses (acetic, propionic, and aconitic acid), lemon juice (citric acid), or cream of tartar.

Combining baking soda with an acid, and a liquid activates it. This kick starts a reaction that produces millions of tiny carbon dioxide in the batter or dough.

The acid not only aids in the production of carbon dioxide, but also works to neutralize the combination to prevent the unpleasant taste of alkalinity from lingering in the finished product (basicity). Therefore, it is important that only the exact amount of baking soda is added as specified in a recipe.

Another thing to remember when working with baking soda is that it reacts quickly with heat and carbon dioxide when incorporated alone. It may escape even before it is able to leaven the batter. Therefore, in order for baking soda to be beneficial, it must be mixed with another ingredient. To delay the carbon dioxide production and prevent it from escaping, either a liquid acid (lemon juice) or a dry acid (cream of tartar) plus liquid should be added.

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Baking powder

Baking powder is another chemical leavening agent. But unlike baking soda, baking powder is a complete leavening agent—it already contains a base and acid to do its job. To put it simply, an acid is no longer necessary because the acid is already built into the mixture. Baking powder begins to function upon contact with a liquid.

Baking powder consists of three components: sodium bicarbonate (baking soda), one or more a dry acid (such as cream of tartar), and inert cornstarch filler. Cornstarch is there as a filler to keep the dry acid and base physically separate from one another. The filler also absorbs excess moisture in the air to prevent caking and/or reduction of its potency.

There are two types of baking powder: fast or single acting powder, and slow or double-acting baking powder

Fast/single acting baking powder produces carbon dioxide as soon as water is added. Hence, a flour mixture made with it should be handled fast and correctly and placed in the oven as soon as possible. Any delay gives the carbon dioxide time to escape, reducing the mixture’s capacity to rise. For each cup of flour, about 1 1/2 to 2 tablespoons of single-acting baking powder is required.

Double-acting baking powder, on the other hand, is slow-acting. This is what most commercial bakers use in their products. Most common are sodium aluminum sulfate and phosphate powder. It releases carbon dioxide twice: first when moistened (in a mixing bowl) and second when heated (in the oven). For each cup of flour, approximately 1 to 1 1/2 teaspoon of double-acting baking powder is necessary.

Cell walls may be stretched and break if too much baking powder is added to a formulation because of an overstretched, collapsed structure and the release of carbon dioxide bubbles.

PHYSICAL (MECHANICAL) LEAVENING AGENTS

The simplest technique of leavening is physical leavening, which includes adding air to a batter or dough mechanically or physically.

Air or steam

Almost all batters and doughs contain some amount of air, which when heated expands and adds to the product’s volume. In “unleavened” baked goods, such as some breads, crackers, or pie crusts, it could be the only leavening agent.

There are several ways to incorporate air as a leavening agent during baking. Creaming sugar and fat, together can add air to a cake. Creaming incorporates air by beating sugar crystals and solid fat (usually butter) in a mixer. This occurs because sugar crystals are capable of physically dissolving through the structure of the fat. As air becomes trapped by the web of sugar and fats, air pockets are created, adding volume to the final baked product. Often, creamed mixtures are further leavened using a chemical leavener, usually baking soda.

Another way to physically leaven using air is by beating egg whites or whole eggs. This is often done when making angel food or sponge cake. Due to their ability to foam when forcefully beaten or whisked, egg whites can leaven baked goods. This is due to the egg white’s capacity to hold air, which is what gives it its function as a leavening agent. The volume of whipped egg whites can grow by up to eight times. This leavening is made possible by albumin and ovalbumin, two proteins found in egg whites. This post further explains this.

Steam

The conversion of water to steam is a physical change, thus, steam is a physical leavening agent in baking. Nearly everything is leavened to some extent by steam. Steam vapor is produced in 1,600 parts for every part of water. Water, juices, milk, or eggs are examples of liquid components that can be used to create steam. Foods such as cream puffs, choux pastry, and popovers rely on steam for leavening. The dough protein expands as a result of the creation of steam, and the egg protein denatures and coagulates to give them their distinctive high volume and hollow interior.

Sometimes steam is injected into the oven at the start of baking. This is to make sure the bread rise higher and the crust is thinner.

References:

M. Wallert, K. Colabroy, B. Kelly, J. Provost (2016). The Science of Cooking: Understanding The Biology And Chemistry Behind Food And Cooking. John Wiley & Sons, Inc..

V. Vaclavik, E. Christian (2014). Essentials of Food Science (4th edition). Springer.

M. Gibson (2018). Food Science and the Culinary Arts. Academic Press.

J. Jay, M. Loessner, D. Golden (2005). Modern Food Microbiology (7th edition). Springer.

W. Zhou, Y. H. Hui, I. DeLyn, M. A. Pagani, C. M. Rosell, J. Selman, N. Therdthai (2014). Bakery Products Science and Technology (2nd edition). John Wiley & Sons, Ltd

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Cocoa powder is produced by removing fat from cocoa liquor, the liquid product after grounding cocoa nibs from the beans of the cocoa tree. This is done by pressing the cocoa liquor using a mechanical or hydraulic press. Cocoa liquor is naturally acidic mainly because it contains acetic and lactic acid. For this reason, the resulting cocoa powder is quite acidic. Its pH level ranges between 5.3 to 5.8.

The hydrogen potential or pH measures how acidic or basic a substance is. A pH of 7 is neutral; a pH lower than 7 is acidic; and a pH higher than 7 is basic or alkaline.

To counter the acidity of natural cocoa powder, an alkaline substance or alkalizing agent can be added before or after roasting of cocoa beans, producing Dutch-processed cocoa powder or alkalized cocoa powder. This process is called the Dutch process (or “Dutching”). Dutch chocolate maker Coenraad Johannes van Houten invented Dutching during the early 19th century.

Aside from decreasing the acidity, the Dutch process also makes cocoa powder darker brown than natural cocoa powder. This is the result of the neutralization of the acid in the cocoa powder. The more alkalizing agent used, the darker the color. Alkalized cocoa powder is also milder (less bitter) and has a more complex flavor profile. Caramel-like molecules such as furaneol, pyrones, pyrazines, and thiazoles are increased with Dutching. Natural cocoa powder, on the contrary, can be astringent and harsh, overwhelming the presence of other flavors.

Many consumers prefer alkalized cocoa powder than natural because it produces better looking and better tasting baked products. Today, alkalized cocoa powder is the main component in modern chocolate and a key ingredient in popular food items such as ice cream.

HOW IT IS MADE

All cocoa, beans, nibs, and liquor that has been treated with an alkali agent are referred to as “alkalized” or “Dutched.” The process entails soaking the cocoa nibs in an alkaline solution. The alkali is used to raise the pH of the beans or nibs from 5.3 to 5.8 to near neutrality at 6.8 to 7.5. This depends on the alkali used and the purpose of Dutching. Numerous alkalizing agents can be used to produce alkalized cocoa. Commonly used include potassium carbonate, sodium carbonate, and sodium hydroxide.

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The process usually aims to change the color and flavor of cocoa powder or cocoa liquor. And to enhance the dispersibility or suspension of the cocoa solids in water.

During the process, the alkali solution is sprayed into a drum after it has been charged with the nibs, and the drum is subsequently slowly dried at a temperature below 212°F (100°C).

USING ALKALIZED COCOA POWDER

Cocoa powder is a frequent ingredient for baking and for drinking with added milk and sugar. However, it is worth noting that the main change with Dutch-processed cocoa powder is that its acidity has been washed and neutralized. With a neutral pH, it does not react with baking soda.

Why?

Baking soda is simply alkaline and needs an acid to completely activate, whereas baking powder contains both an acid and a base. Hence, recipes that include baking soda (sodium bicarbonate) must also include an acid, such as cream of tartar. Hence, baking soda is often paired with natural cocoa powder to activate it.

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Recipes that use alkalized cocoa powder, often calls for baking powder, which, too, has a neutral pH.

Many chocolate recipes that do not call for a leavening agent can use both cocoa powder options. Either type of cocoa powder can be used in foods such as ice cream and sauces. Although there will still be changes in color and flavor when using natural versus alkalized cocoa powder.

The post What Is Alkalized Cocoa (Dutch-Processed)? appeared first on The Food Untold.

Bread is one of the first foods made by humans. History suggests that the first bread was baked thousands of years ago. It was produced using a few ingredients—crushed grains with water. And then baking was done by spreading the mixture on stones to bake in the sun. Flour making was very simple back then. In Upper Paleolithic in Europe, grains would be ground using a combination of a stone mortar and pestle. As technology advanced, different processes of grinding to produce flour were invented. Like for example, the ancient Greeks fed grains between millstone and ground into powder by a mechanism powered by water. Flour created by this method was finer that flour made by hand.

Before the 20th century, flour did not really look like the ones we use today. The outer layers of the grain, known as the germ and bran, were not removed or significantly broken down by simply grinding the grains into a powder. This form of grain is referred to as “whole grain”, which commonly produces darker flour. The bread created with this flour still contains all of the grain’s original nutrients. However, the higher classes had traditionally preferred the whiter flour grades, which were more expensive.

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The process of turning grains into flour has come a long way. Today, there are several types of flours in the market. These include unbleached and bleached flour.

What is the difference between the two, anyway? And which one is better?

WHY BLEACH FLOUR?

Well, unbleached flour ages over time as it naturally whitens and improves its baking quality. Freshly milled flour contains significant amounts of xanthophyll along with other pigments. It is a class of oxygen-containing carotenoid pigment responsible for the off-white color (light color) of fresh flour. Yellow-colored are not exactly the type of flour consumers would find appealing. However, exposure to air oxidizes the carotenoid xanthophylls during storage, eventually turning the color of flour from yellow to white. But the bad thing is that natural aging is impractical. It is time consuming. It takes 2 to 3 months of storage before flour becomes white. For millers, it is not ideal to wait that long. Furthermore, natural aging also requires a large storage space, there is the risk of contamination, and results may not be consistent.

For a businessman, you would want to have your product ready for the market as quickly as possible. This is where flour bleaching comes in, a process first introduced in the 1906 Pure Food and Drug Act.

Bleaching is a chemical treatment that speeds up the aging process of flour. In this process, the yellow carotenoid xanthophyll is oxidized, turning it into colorless compounds. This is similar to bleaching carotenoid or chlorophyll pigments in milk.

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There are several maturing agents that can be used to bleach flour. These include nitrogen peroxide, benzoyl peroxide, chlorine gas, chlorine dioxide, and nitrogen trichloride. The Food and Drug Administration (FDA) has approved the use of these additive in flour. But there should be extra caution when bleaching since maturing agents affect the properties of the flour. For example, potassium bromate strengthen the gluten, while others like benzoyl peroxide weakens it.

UNBLEACHED VS. BLEACHED FLOUR? WHICH ONE IS BETTER?

As you might already have figured out, unbleached flour is also bleached, but in the old-fashioned natural way that takes several months to complete. With that having said, is bleached flour better? Well, each type has its own advantages.

Bleaching is more than just turning flour whiter—it also improves the baking performance of flour. Bleaching softens the flour, which in turn generally produces improved baked products—better volume, softer, and brighter color than products made with unbleached flour. For this reason, bleached flour is ideal for muffins, cookies, pancakes, pie crusts, waffles, quick breads.

Another advantage of bleached flour is that it is user-friendly during baking. Gluten is a three-dimensional, viscoelastic structure produced by certain proteins. It determines the texture and volume of the finished product. By adding bleaching or maturing agent, the proteins in the flour become modified to develop the gluten network that makes the dough less sticky and easier to knead.

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Unbleached flour, on the other hand, has denser grain and tougher texture. But this is advantageous if the baked product requires more structure to hold their shape better. With that having said, unbleached flour is ideal for pastries, yeast breads, eclairs, popovers, and cream puffs. Another advantage of unbleached flour over bleach flour is its nutrient content. Some varieties of unbleached flour contain more vitamin E, fiber, vitamin E, copper, manganese, and some antioxidants.

The post Unbleached Or Bleached flour: The Difference appeared first on The Food Untold.

The majority of food items have their expiration date, and bread is no exception. Like most baked products, bread is an example of semi-perishable food. It does not require refrigeration for a short while. It may last 3 to 5 days at room temperature or longer. There are several signs to tell if bread has already gone bad. Bad mold growth is usually the obvious sign that it is time to discard a loaf of bread. But how long until bread begins to mold?

Bread takes 5 days or so until it begins to mold. This depends on several factors such as the storage conditions. Is it humid and warm? Bread can last up to 5 days more in the refrigerator. But this is not ideal (unless you are making breadcrumbs) because the temperature is harsh for the starch molecules. Starch molecules are made up of long chains that shorten and firm up when they cool, a process known as staling. This is visible when stale products become softer when heated and firm up again after cooling.

Another factor is the ingredients of the bread. Usually, homemade bread grows mold much quicker than store-bought. This is because store-bought bread typically contains many preservatives that extends shelf life. Examples of these include potassium sorbate, sorbic acid, and sodium benzoate.

WHY MOLDS GROW ON BREAD?

Mold growth is the most common cause of microbiological spoilage in bread. They are fungi that grow in the form of multicellular filamentous structures known as hyphae, which helps absorb and break down nutrients. Molds present on bread are usually off-white, and sometimes with fuzzy black, green, or pink spots.

Because molds and mold spores are thermally inactivated during the baking process, bread straight out of the oven is mold-free. Molds reproduce through spore. Mold spores are tiny invisible to the naked eye. And you may not realize it, but mold spores are virtually everywhere— in your kitchen and even inside bakeries.

Sure, bakeries can be as hygienic as possible, but the environment is not sterile because of the ingredients used for baking. Dry ingredients, specifically flour, contain mold spores, and flour dust spreads easily through the atmosphere. Just a gram of flour can contain as many as 8000 mold spores. Mold spores present in the atmosphere during chilling, slicing, packaging, and storage contaminate bread after baking.

But mold spores are just one of the requirements in order for molds to grow. The appropriate temperature, moisture, and food (bread) must also be available, all of which can be easily sourced in a piece of bread at room temperature. This is why molds do not grow if the bread crust is rather dry and the relative humidity of the atmosphere is below 90%. Molds will grow quickly in a damp environment, especially on a loaf within a wrapper. This is especially true if the bread is wrapped while still hot from the oven, causing droplets of water to condense on the inside surface of the wrapper.

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When bread is cut, the interior, which is more vulnerable becomes infected with mold. The moist, cut surfaces of sliced, wrapped bread are a great substrate for molds to develop on. Furthermore, the packaging prevents moisture to escape.

CAN YOU EAT MOLDY BREAD?

Some people have tried removing the moldy portion of a bread, and got away with it. But this is totally not recommended.

There are more than 10,000 different types of molds. In bread spoilage, the 5 most common types responsible are Aspergillus, Fusarium, Mucor, Penicillium, and Rhizopus. Rhizopus (nigricans) Stolonifer is the most frequent type of black bread mold. It has a fluffy look due to the presence of white cottony mycelium and black sporangia.

As earlier mentioned, (storage) temperature has an effect on the growth of mold in bread. This also affects the type of mold that would grow. Neurospora sitophila, a reddish mold, grows in bread that has been stored at high humidity or wrapped while still warm. In tropical countries, such as India, Aspergillus spp is the dominant spoilage mold. Penicillium spp. is usually blue or green, flat and spreads slowly.

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Aside from spoilage, some molds pose a serious threat to public health because they can produce mycotoxins. Mycotoxins are secondary metabolites that are toxic that, when ingested may cause illness or death.They are extremely resistant and can withstand the heating method used to eliminate molds. While directly eating mold-contaminated bread may lead to exposure to mycotoxins, consuming the products of animals fed contaminated bread may also result indirectly in mycotoxin exposure.

The truth is that eating a moldy bread may be poisonous if sufficient amount of mycotoxins is present. And discomforts vary depending on the quantity of toxin ingested, the length of exposure and the age and health condition of the person. In some animals, bread molds are highly toxic. According to studies, 10% of Aspergillus spp. and Penicillium spp. are harmful to mice.

Today, consumers are more likely to reject the entire loaf than to cut away the clearly moldy section and eat the rest, as was once typical in the past. And since it requires a considerable quantity of mold growth to form mycotoxins, molds and mycotoxins pose little harm to public health in developed and developing countries

PREVENTING MOLD GROWTH

Proper storage is the key to prevent mold growth and extend the shelf life of bread. The idea is to keep the bread from being exposed to what molds require to grow: moisture, temperature (warmth), and light. This is especially true if your home is warm and humid. Ideally, you should have a cool, dark, and dry place to store bread. If not, there are several containers that work very well in keeping bread fresh for several days.

Brown paper bag

First is brown paper bag. This is the container most bakeries used for their products, and for a good reason. Paper bag prevents bread from going moldy because of its permeability—it allows moisture to escape. This is why it works great for breads with a hard crust. While closed allows air to circulate inside the bag, helping maintain the crusty crust and moisture in the crumb.

One problem with paper bag is that it makes bread to go stale much quicker. For this reason, bread in a paper bag should be consumed within 2 to 3 days before it becomes stale.

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Linen bag/ cloth bread bag

If you do not have a brown paper bag, another great option is a linen bag or cloth bread bag. It helps prevent mold growth in a similar way. Just like a paper bag, a linen bag is made of a material that allows the content to be breathable. It allows moisture to circulate to keep the bread crusty and fresh for 2 to 3 days.

Bread box

A bread box is great because it keeps bread crust crunchy, while keeping the center soft and chewy. Its inside is dark and dry, and the small holes provide a good balance of moisture and enough ventilation. Bread boxes are mainly used to store bread and keep them fresh for a few days. To prevent mold growth, ensure there is ample room for good ventilation. To make sure of this, do not overload the bread box. Doing so will lead to an increase in humidity. Or better yet, use a bigger bread box.

If you do not have a bread box, a kitchen cabinet will do. A kitchen cabinet should provide proper air circulation to prevent mold growth. Just make sure to place the bread first in a linen bag or an open plastic bag.

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